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J Biol Chem. 2003 Oct 24;278(43):42427-34. Epub 2003 Aug 14.

Store-operated cation entry mediated by CD20 in membrane rafts.

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Immunology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary Health Sciences Center, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada.


B cell activation requires sustained elevation of cytoplasmic free calcium, achieved by influx through store-operated calcium (SOC) channels. The molecular identity of these channels is not known. Ectopic expression of the raft-associated tetraspan protein CD20 in Chinese hamster ovary cells introduced a novel SOC entry pathway that was permeable to strontium as well as to calcium. The activity of this SOC pathway was abolished by deletion of a cytoplasmic sequence in CD20 essential for its efficient raft localization. Strontium-permeable SOC channels were detected in B cells, and B cell receptor-stimulated influx was significantly reduced by downregulation of CD20 expression using short interfering RNA and also by cholesterol depletion. This is the first evidence that raft-associated CD20 constitutes a component of a SOC entry pathway activated by the B cell receptor.

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